EXTREMELY LOW-BIRTH-WEIGHT INFANT
Extremely low-birth-weight (ELBW) infants are defined as infants weighing less than 1,000 g at birth (Mandy, 2016; Sherman, 2014). In 2013, 8% of the approximate 550,000 preterm infants born in the United States were low-birth-weight infants (Mandy, 2016). Less than 1% of the low-birth-weight infant population consists of ELBW infants (Mandy, 2016; Morris, 2015). Although ELBW infants account for a small percentage of overall births, they are generally the most critically ill and at the highest risk for death and disability (Glass et al., 2015; Sherman, 2014). Care of the ELBW infant is complex and requires understanding the ELBW subgroups and the pathophysiologic processes associated with each subgroup (Papageorgiou & Pelausa, 2014). Care for these infants requires expert management beginning in the delivery room and continuing in the neonatal intensive care unit (NICU). Careful consideration is necessary when providing respiratory, thermoregulatory, and nutritional support, and neuroprotective care (Morris, 2015; Sherman, 2014).
Prematurity, defined as birth before 37 weeks of gestation, is a significant contributor to infant and child morbidity and mortality and is associated with one third of all infant deaths in the United States (Glass et al., 2015). The rate of premature births in the United States had been on a steady rise during the 1990s and early 2000s, but had begun to decrease annually in the early 2010s. However, in 2015, the U.S. premature birth rate increased for the first time in 8 years from 9.57% to 9.63% (March of Dimes, 2016). Major risk factors for preterm births include multiple births (e.g., twins or triplets), history of preterm delivery, stress, infection, smoking and/or illicit drug use, and extremes in maternal age (e.g., mothers younger than 16 years old, mothers older than 35 years old; Mandy, 2016; Morris, 2015).
Of the 450,000 to 500,000 preterm births in the United States each year, fewer than 1% of these infants are ELBW (Mandy, 2016; Morris, 2015). ELBW infants can be classified into two subgroups: The first ELBW group consists of extremely premature infants who are appropriate for gestational age, and the second ELWB group consists of intrauterine growth–restricted infants who are small for gestational age, but not necessarily very premature (i.e., less than 27 weeks gestational age; Papageorgiou & Pelausa, 2014). Understanding the differences between these two subgroups is essential as the different pathophysiologic processes associated with each group may yield different responses and outcomes to the care provided.
Although perinatal care, technology, and understanding of the pathophysiology and needs of the ELBW infant have improved, ELBW infants remain at high 141risk for death with 30% to 50% mortality and high risk for severe impairment with 20% to 50% long-term morbidity in survivors (Glass, 2015; Papageorgiou & Pelausa, 2014; Sherman, 2014). The risk of death increases with decreasing birth weight and gestational age, and both are associated with increasing immaturity. The infant mortality rates per 1,000 live births in the United States in 2013 were 124.6 for infants weighing 750 to 999 g, 394.3 for those weighing 500 to 749 g, and 853 for those weighing less than 500 g (Mandy, 2016